Plans for future research again follow both the mechanism of segregation distortion and the population dynamics of the phenomenon. Cytologically, we are using BAS to better define spermatogenesis at the level of light microscopy, and we are in the process of perfecting this technique. Genetically, we are mutagenizing and selecting for recessive male steriles in the regions of Sd and Rsp, hoping to fing a male-sterile locus associated with defects in sperm histone transition and thereby identifying either the structural gene for sperm histones or a regulatory gene involed in the transition. With respect to population genetics, we are continuing studies of Hiraizumi's long-term population cage with special emphasis on assessing the amount of permanent linkage disequilibrium built up. From a theoretical point of view, we are collaborating with Brian Charlesworth on a mathematical analysis of a model of segregation distortion that incorporates all of the known biological facts.